Poly crystallization from toluene

An analysis of the overall crystallization rate with composition requires that the comparison be made either at constant undercooling or at one of the nucleation temperature quantities, T / T AT or T /T(AT). This requirement is essential because of the importance of nucleation to the crystallization process. The overall crystallization kinetics of a variety of polymer-diluent systems have been reported. Many different relations between the overall crystallization rate and composition have been observed. For example, as is shown in Fig. 13.17 there is a continuous decrease in the crystallization rate with dilution for linear polyethylene-a-chloronaphthalene mixtures.(42) The results for poly(trans-1,4-isoprene) in methyl oleate follow a similar pattem.(80) In contrast, the rates for poly(dimethyl siloxane) crystallizing from toluene, at compositions V2 = 0.32 to 0.79, are the same at all undercoolings, but are faster than that of the pure polymer.(78) Another example is found with poly(ethylene oxide)-diphenyl ether mixtures.(77) In this case the crystallization rates for the pure polymer and composition = 0.92 to 0.51 are the same. However, the rates for the more dilute mixtures, V2 = 0.04 and 0.30 are lower. For poly(decamethylene adipate)-dimethyl formamide mixture the rates for the pure polymer and V2 = 0.80 are the same.(77) The mixture of isotactic poly(propylene) with dotricontane shows interesting behavior.(81) At all undercoolings studied, the crystallization rate initially decreases with dilution, reaches a minimum in the range V2 — 0.7 (a maximum in ti/2) and then slowly increases with further dilution, up to V2 = 0.10. 

Cohen et al. (1990) studied a poly(styrene)-poly(ethylene) (PS-PE) diblock that was solvent cast from toluene. Crystallization within microphase-separated PE spheres occurred when solvent-casting was done above the PE block melting temperature, Tm (see Fig. 5.2). When solvent was removed below Tm crystallization did not occur within spherical microdomains, instead TEM and SANS experiments suggested an irregular structure. Nojima et al. (1994) suggest that crystallization from the melt in this sample occurred within the microphase-separated block in the former case due to the high molecular weight of the... 

Figure 13 Optical absorption of the PDA poly-4BCMU in three differently ordered states (a) solution in chloroform (b) gel from toluene (dense homogeneous films cast from solution have similar, though slightly less structured, spectra) (c) single crystal.

Growth rate studies, utilizing a light scattering method, have also been reported for molecular weight fractions of poly(ethylene oxide) crystallizing from a 0.01 wt percent solution of toluene. The role of chain length is illustrated in Fig. 13.20 as a... 

Fig. 13.20 Plot of log G against crystallization temperatures for molecular weight fractions of poly(ethylene oxide) crystallizing from 0.01 wt% toluene solution. Molecular weights 5.6 x 10" 1.05 x 10 1.60 x 10 3.25 x 10 O 7.70 X 10. (From Ding and Amis (54))...

FIGURE 1.14 Viscosity as a function of polymer concentration of a solution of a 50 50 random copolymer, poly(w-hexylisocyanate-co-n-propylisocyanate) (M , =41,000 g/mol) in toluene, encompassing the isotropic, biphasic, and anisotropic (liquid crystal) regimes. (Adapted from Aharoni [1980a].)... 

Figure 11.11 TEM image of PM-PDMS-PM crystal plates. (Reprinted from Polymer, 48,14, J. Wang, J.H. Horton, G. Liu et al, Polymethylene-Z /<9c -poly(dimethyl siloxane)-Z /oc/ -polymethylene nanoaggregates in toluene at room temperature, 4123-4129, 2007, with permission from Elsevier.)...

The self-seeded crystallization of high-molecular-weight poly(ethylene oxide) from dilute toluene solutions by static and dynamic light-scattering techniques indicated that the radii of the crystals grow in a linear manner (77). The rate constant. 

Some of the first third order NLO studies of CPs were carried out on the poly(di-acetylenes) (P(DiAc)). One of the first such studies, on P(DiAc)-toluene sulfonate (PTS) single crystals, carried out by Sauteret et al. [502], revealed third order bulk NLO susceptibilities x fzzzz) polymer chain axis) of 1.6 X 10 ° esu at 2.62 pm and 8.5 X 10 ° esu at 1.89 pm. These values have as yet been exceeded only by one study, that of Drury on oriented Durham P(Ac) [503], in which a value for x zzzz> (Z= polymer chain axis) of 10 esu at 1.9 pm. However, this value of the susceptibility was inferred from THG data somewhat indirectly. Dennis et al. [504] reported off-resonant x xyyx values of 7 X 10 esu for solutions of various P(DiAc), extrapolated to pure substance and determined via DFWM at 532 nm. 

Figure 3.8 Single crystal of poly(ethylene oxide) grown from 0.01% toluene solution at 25°C. Sectors are revealed by decorating the basal surface with short polyethylene crystals as described in the text. While the crystal appears to be square, growth faces are 120 in a monoclinic system. From Chen et al. [8] with permission from John Wiley Sons, Inc.

---